Valve and a method of making the same



June 13, 1939. F.. c CRAWFORD 2,162,063

VALVE AND METHOD OF MAKING THE SAME Filed Feb. 29. 1936 Patented June13, 1939 UNITED STATES PATENT OFFICE I Frederick C. Crawford, Cleveland,Ohio, assignor to Thompson Products, Incorporated, Cleveland, Ohio, acorporation of Ohio Application February 29, 1936, Serial No. 66,339

Claims.

This invention relates to a valve and to a method of making the same,and more particularly to the manufacture of a valve having a layer of asurface alloy formed over the founda- 5 tion metal.

It has heretofore been proposed to provide surface alloys of metals,such as alloys of chromium and iron, by a cementation process. Thepatent to Kelley No. 1,365,499, dated January 11, 1921,

for instance, discloses a method for chromizing foundation metals, suchas iron, nickel, molybdenum, or tungsten, according to which thefoundation metal is heated in contact with powdered metallic chromiumunder non-oxidizing condi- 25 tions to a temperature of about 1200 Ato1350 C.

The powdered metallic chromium may be admixed with a refractory, inertmaterial, such as alumina or magnesia, in approximately equalproportions, or powdered aluminum may be admixed with the chromium toprevent oxidation of the chromium. The cementation takes place at atemperature below the melting point of either the chromium or of theferrous metal or ferrous metal alloy foundation.

If such a chromizing process is applied to valves, I have found thatbecause of the large grain structure of the chromized metal, the nishedarticle has but little strength and hence cannot be satisfactorily usedunder tension or 3o where subjected to repeated stresses. It istherefore not feasible to use the process of the Kelley patent directlyin the chromizing of valves because if the valve is treated in afinished condition, it would then have inherent weaknesses due to largegrain size.

I have now found; however, that if a billet or slug is first chromizedin accordance with the process of the Kelley patent and then severelyWorked, as by extruding, forging, and the like,

such heavy mechanical work performed on the chromized foundation metaltends to break up the grain size, at the same time producing a valvehaving a surface layer of an iron-chromium alloy that is heat andcorrosion resistant. Other surface alloys, such as those of aluminum,may be produced by the cementation process on other foundation metals,such as nickel, molybdenum, tungsten, or their ferrous alloys.

5@ It is therefore an important object of this invention to provide amethod of making a valve having a surface alloy of desiredcharacteristics.

It is a further important object of this invention to provide a valvefor` internal combustion engines having a surface layer of an alloy of(Cl. Ztl-156.7

iron and chromium, which is heat and corrosion resistant.

It is a further important object of this invention to provide a methodof making a chromized surface valve,l starting with a chromized surface5 billet and forming the stem and head by a combined extrusion andforging operation.

It is a further important object of this invention to provide a valvehaving afsurface alloy of iron and chromium, the grain size of which has10 been reduced by heavy mechanical working of the metal from which thevalve is formed.

Other and further important objects of this invention will becomeapparent from the following description and appended claims. l5

This invention (in a preferred form) is illustrated in the drawing andhereinafter more fully described.

On the drawing:

Figure l is a longitudinal sectional view 20 through a die, with aplunger in elevation, showing the method of extruding a billet having asurface alloy to form a valve of my invention.

Figure 2 is a longitudinal sectional view of a chromized billet or slug.25.

Figure 3 is a longitudinal sectional view of a partially formed valveafter thel extrusion process has taken place.

Figure 4 is a longitudinal sectional view of a valve having a headthereon finished by a forging 30| operation. Y

As shown on the drawing:

The reference numeral l0 indicates a billet or slug comprising afoundation metal ll and a surface alloy l2 formed thereon by acementation 35. process such as described in the above identified Kelleypatent. The foundation metal Il may be iron or steel, nickel,molybdenum, tungsten or an alloy of any one or more of these with iron.The surface alloy l2 is an alloy of the foundation 40. metal and someother metal, such as chromium, aluminum, or the like. Since an alloy ofiron and chromium has particularly good resistance to heat and corrosionand therefore is especially adapted for use in the manufacture ofvalves, the 45. invention willl be described with reference to a valvehaving a chromized surface. It will be understood, however, that othermetals may be used in the forming of the surface alloy.

The heated billet l0 is placed in a recess I3 of 50, a die block l toeffect the extrusion of the metal of the billet. The recess i3 isslightly larger in diameter than the diameter of the cylindrical billetit, the inner wall of the recess tapering at the bottom to provide agenerally conically Ation 22.

shaped neck-portion Il and a bore I6 of reduced diameter. The die block.Il is suitably formed in two parts, an upper member I8 constituting thedie proper and a lower member I1 provided with a passage I8 for thecirculation of a cooling fiuid.

A plunger I8 carrying a cylindrical head 20 of substantially the samediameter as that of the recess I3 is adapted to be forced down into saidrecess to snugly fit the same and extrude metal from the billet l0through the throat I5 and bore I6. In its extreme lower position, thehead of the plunger assumes the position indicated in dotted lines inFig. l, the length of travel of the plunger being such as to leave aportion, indicated by the reference numeral 2|, of the billetunextruded.

After the extrusion process, the partially formed valve is in the formillustrated in Fig. 3 and comprises a head portion 2l and a stem por-'I'he surface alloy layer I2 of iron and chromium extends over thepartially formed head portion 2| and down along the stem portion 22, thethickness of the layer tapering off toward the extremity of the stemportion. Although the surface layer I2 is shown in Fig. 3 as extendingthe full length of the stem 22 and over the end thereof, it will beunderstood that it is not necessary for the surface alloy layer tocompletely cover the stem. Also, for purposes of illustration,

the relative thickness of the surface alloy layer is greatlyexaggerated. In the case of the original billet, for instance, the depthof the penetration of the iron-chromium alloy may be only between 0.030and 0.040 inch. This amount of penetration can be obtained in the caseof an iron -or steel foundation metal by heating the billet undernon-oxidizing conditions or in a g vacuum in contact with powderedmetallic chromium to a temperature of from 1200 to 13507 C. for aboutfour hours or more.

The partially finished valve head 2I is next subjected to a forgingoperation, or a combined upsetting and forging operation to produce anenlarged head portion 23 (Fig. 4) having a conical seat engaging surface24. The usual machining operations may be performed to provide afinished valve and a portion of the stem may be milled out, as at 25, toprovide a reduced portion for receiving the valve spring retainer lock.In the nshed valve, the layer of surface alloy I2 will be slightlythicker over the top of the head portion and the thickness will slightlydiminish toward the extremity of the stem protion 22.

Due to the heavy mechanical work performed in the extruding and forgingoperation, the grain size of the iron-chromium alloy and of the ferrousfoundation metal or alloy is considerably reduced, refining the metal togive maximum strength and fatigue resistance.

I'he resulting valve is therefore strong and, on the head and part ofthe stem at least, heat and corrosion resistant. Furthermore, thechromized surface of the valve possesses considerable hardness, whichreduces wear in the valve stem guides.

The foundation metal of the billet used in forming a valve of myinvention may suitably be a chrome-nickel steel,l such as SAEspecifications No. 3140, or a common carbon steel, such as SAEspecifications No. 1020. Other metals, however, may be used for afoundation metal, or alloys of such other metals as nickel, molybdenum,or tungsten. In fact any of the metals commonly used in the commercialmanufacture of valves may be employed in my method as the foundationmetal.

I am aware that many changes may be made and numerous details ofconstruction 'may be varied through a wide range without departing fromthe principles of this invention, and I, therefore, do not purposelimiting the patent granted hereon otherwise than necessitated by theprior art.

I claim as my invention:

l.. The method of making a chromized` valve, which comprises chromizinga cylindrical billet to a depth of 0.03 to 0.04 inch and extruding saidbillet to form a stem and head having a chromized surface layer taperingoff in thickness from the head toward the stern.

2. The method of making a one-piece valve having a thin surface alloy,which comprises providing a metal billet or slug with the desired thinsurface alloy by a cementation process and extruding said billet to formsaid valve and reduce the grain size of the metal thereof and of thesurface alloy.

3. A one-piece poppet valve comprising a head and a stern of ferrousfoundation metal having a thin cementized surface alloy thereondifferent from said foundation metal, said stem having been extrudeddown from a billet of the foundation metal and the surface alloy toreduce the grain size of the alloy.

4. A one-piece poppet valve comprising a head and a stem of ferrousfoundation metal having a chromized surface alloy of only a fewhundredths of an inch in thickness and of inwardly decreasing chromecontent, said stem having been worked down from a billet ofthe-foundation metal and surface alloy, and the head formed therefrom bya forging operation to greatly reduce the grain size of the chromizedalloy.

5. The method of making a one-piece poppet valve having a thin surfacealloy which comprises chromizing a metal billet to a depth of a fewhundredths of an inch, and extruding said billet to form a stem and headhaving a chromizedsurface of a reduced grain size.

FREDERICK C. CRAWFORD.

